class Solution
{
public:
    vector<int> twoSum(vector<int>& nums, int target)
    {
        unordered_map<int, int> hash;
        for (int i = 0; i < nums.size(); i++)
        {
            int x = target - nums[i];
            if (hash.count(x)) return { hash[x], i };
            hash[nums[i]] = i;
        }
        return {};
    }
};